Imaging of gastrointestinal
perforation
RAD Magazine, 38, 448, 33-34
by Mr J B Haddow
Specialist registrar in general surgery1
Dr M J Steward
Consultant gastro-intestinal radiologist2
Mr H Mukhtar
Consultant colorectal surgeon1
Dr D Murray
Consultant gastro-intestinal radiologist2
Departments of Surgery1 and Radiology,2
The Whittington Hospital, London
email: [email protected]
Gastrointestinal (GI) perforation is a common
surgical emergency requiring accurate and timely
diagnosis. It can occur at any point along the
gastrointestinal tract, caused by peptic ulcer disease, inflammation, trauma (blunt or penetrating), iatrogenic factors, foreign body or neoplasm.1
Ascertaining the site of perforation can be difficult, given the nonspecific nature of the presenting symptoms. Plain radiography is generally the
first line investigation, but is only sensitive in
50-70% of cases.2 Multidetector computed tomography (MDCT) has an 86% accuracy in predicting
the site of perforation.3
This article reviews and illustrates the pertinent anatomy and the imaging features of GI
perforation.
Radiological anatomy
The transverse mesocolon can be identified on CT as a fatty
plane that extends from the uncinate process of the pancreas to the transverse colon and contains the middle colic
vessels. This divides the peritoneal cavity into supra and
inframesocolic compartments, which is useful in distinguishing between upper and lower GI perforations.
Gas escaping from the stomach or first part of the duodenum settles in the supramesocolic compartment, whereas
gas escaping from the distal small bowel and large bowel
settles in the inframesocolic compartment. In perforations
of the second and third parts of the duodenum, ascending
and descending colon and middle third of rectum, gas may
escape into the retroperitoneal compartment, usually the
anterior pararenal space.
Radiological free gas signs
Plain radiography can reveal GI perforation by demonstrating the Rigler sign (gas outlining both sides of the bowel),
football sign (oval shaped peritoneal gas), increased lucency
in the right upper quadrant (gas accumulating anterior to
the liver) or the triangle sign (triangular gas pocket between
three loops of bowel).
On CT, the ‘ligamentum teres sign’ (gas outlining the
intrahepatic fissure and ligamentum teres) is often elicited
in perforations of the duodenal bulb or stomach. The periportal free gas sign (PPFG; gas locules around the portal
tract) shown in figure 1 correlates with an upper GI perforation. The ‘falciform ligament sign’ (free gas or a gas-fluid
level crossing the midline and accentuating the falciform
ligament) is seen mainly in perforations of the stomach, duodenum, jejunum and ileum.
Gastrooesophageal junction
Perforations near the gastrooesophageal junction (GOJ) can
be spontaneous, or due to peptic ulcer disease, neoplasm or
trauma (iatrogenic or foreign body). Spontaneous idiopathic
oesophageal perforations can occur after an episode of severe
retching. Known as Boerhaave syndrome, the perforation
usually occurs on the more vulnerable left side of the distal
oesophagus just above the GOJ, leading to sepsis, mediastinitis and shock. CT demonstrates the extent of free gas
and fluid collection in the neck, but may not be able to
determine the site of the perforation.
Approximately one in 3,000 endoscopies cause an iatrogenic perforation usually of the cervical oesophagus or
hypopharynx, but can also occur in the lower oesophagus
when associated with intervention, stricture or diverticulum.
Stomach and duodenum
The common causes of gastroduodenal perforation are peptic ulcer disease, neoplasia and postoperative anastomotic
leaks. Perforations of the anterior wall of the stomach or
duodenum can perforate into the peritoneal cavity causing
peritonitis, whereas perforations of the posterior wall are
usually contained or walled-off.
On CT, two findings are indicative of the site of a gastroduodenal perforation: a discontinuity in the luminal wall,
and/or tiny extraluminal gas bubbles in close proximity.
Other supporting features include bowel wall thickening,
enhancement and perigastroduodenal inflammatory change.
In upper GI tract perforations, free gas accumulates more
frequently around the portal tract, giving the PPFG sign.
This is due to the anatomical relationship between the portal tract and the gastric antrum or duodenal bulb, and is
considered the best distinguishing feature between upper
and lower GI tract perforations.
Another localising sign is fluid seen between the duodenum and pancreatic head, which is strongly associated with
local perforation. The distribution of gas within the
peritoneum is less specific at localising the site of
the perforation.
Small bowel
The aetiology of small bowel perforation includes obstruction, inflammatory conditions, ischaemia, infarction, trauma,
neoplasia and iatrogenic.
Hyperaemic bowel wall thickening, free peritoneal fluid
and extraluminal gas or contrast medium are the commonest CT findings when perforation is caused by obstruction.
However, the absence of free peritoneal gas does not exclude
perforation. Sometimes a small amount of peritoneal fluid is
the only positive sign.
In acute inflammatory conditions such as Crohn’s disease
or small bowel diverticulitis, the perforation may be uncontained, leading to peritonitis or may be walled-off with
abscess formation. A perforated Meckel’s diverticulum is
rare but should be considered when supra or infra mesocolic gas is found with hyperaemic bowel wall thickening
and mesenteric oedema.
Jejunal diverticulitis is rarer still, but may be considered
when MDCT reveals an asymmetrical focus of small bowel
wall thickening at the site of an out-pouching on the mesenteric side of the jejunum.
Perforation caused by blunt trauma is the result of the
shearing forces from rapid deceleration occurring around fixation points of the small bowel, eg the ligament of Treitz. In
this situation, CT shows bowel wall thickening, pneumatosis,
free gas or a focal fluid collection adjacent to the injured
segment of bowel.
Ingestion of foreign bodies rarely cause perforation, but
when they occur, they tend to be at narrowed or angulated
segments of the ileum, with associated focal fluid collection
and gas bubble signs on the CT.
Iatrogenic small bowel perforation can occur during
laparoscopic surgery, especially in the presence of adhesions,
but may go unnoticed for some days resulting in a delayed
presentation. Chemotherapy very rarely can cause pneumatosis (gas within the bowel wall) without full thickness
perforation (figure 2).
The small bowel is also susceptible to late-stage posttransplant lymphoproliferative disorder (PTLD), where the
jejunum may perforate as a result of neoplastic infiltration.
Appendix
Appendicitis is the commonest cause of appendiceal perforation, resulting in a phlegmon, wall thickening and abscess
formation. Specific signs pointing to this aetiology are a
swollen appendix with peri-appendiceal infiltration, ascites,
abscess and appendicolith.
Colon
Colonic perforation has a high mortality which is best mitigated by prompt diagnosis and treatment. Causes include
diverticulitis, neoplasm, foreign body, obstruction, iatrogenic
or anastomotic leak (figure 3).
In colonic perforation the non-localising sign of generalised pneumoperitoneum can occur. If, however, free gas is
confined to the pelvis, then the site of perforation is usually the colon. Free gas solely confined to the supramesocolic compartment is unusual in colonic perforation.
In sigmoid perforations, wall thickening and pericolonic
stranding may be the only localising signs. Occasionally, a
sigmoid diverticulum can perforate into the mesosigmoid,
allowing gas to track into the retroperitoneum (figure 4).
Other CT findings in colonic perforation are a complex mass,
inflammatory change, extraluminal fluid, and bowel wall
thickening around the perforation site.
Colonoscopy has a perforation rate of one in a thousand
patients. Intraperitoneal perforation results in pneumoperitoneum, whereas perforations of the posterior walls of the
sigmoid, descending and ascending colon, result in free gas
within the retroperitoneum, often the anterior pararenal
space. CT colonography has a perforation rate four times
lower and of these perforations only one in nine require surgical treatment.4
Colonic carcinoma that invades the serosal fat has an
increased risk of perforation with abscess formation and gas
leak. Other associated signs are diffuse or focal bowel wall
thickening and pericolonic stranding.
Anorectum
The lower third of the rectum and the anal canal are
extraperitoneal and perforation is most commonly seen due
to trauma or anastomotic leak. Cross-sectional imaging,
especially magnetic resonance imaging, is useful in evaluating the extent of the injury and the involvement of the
sphincter, which guides management. Free gas (emphysema)
is a rare finding.
Summary
Gastrointestinal perforation can occur throughout the GI
tract. Imaging has a vital role to play in the early diagnosis
and localisation of the site of the perforation, which has a
direct bearing on the definitive management. CT has a high
sensitivity and specificity, and can demonstrate localising
signs such as supra or inframesocolic or retroperitoneal free
gas, periportal free gas, local gas bubbles, focal bowel wall
thickening or discontinuity, local inflammatory changes and
abscess formation. Pitfalls should also be considered such
as the absence of free gas in small bowel perforation.
Gastrointestinal perforation is a serious condition and a
multidisciplinary approach will ensure early diagnosis and
timely management.
References
1, Furukawa A, Sakoda M, Yamasaki M, Kono N, Tanaka T, Nitta N et
al. Gastrointestinal tract perforation: CT diagnosis of presence, site and cause.
Abdom Imaging 2005;30(5):524-34.
2, Singh J P, Steward M J, Booth T C, Mukhtar H, Murray D. Evolution
of imaging for abdominal perforation. Ann R Coll Surg Engl 2010;92(3):182-8.
3, Hainaux B, Agneessens E, Bertinotti R, De Maertelaer V, Rubesova E,
Capelluto E et al. Accuracy of MDCT in predicting site of gastrointestinal
tract perforation. AJR Am J Roentgenol 2006;187(5):1179-83.
4, Burling D, Halligan S, Slater A, Noakes M J, Taylor S A. Potentially
serious adverse events at CT colonography in symptomatic patients; national
survey of the United Kingdom. Radiology 2006;239(2):464-71.
FIGURE 1
Axial MDCT demonstrating gas locules around the
portal tract, periportal free gas (PPFG; arrow), suggesting upper gastrointestinal perforation.
FIGURE 2
Axial MDCT depicting extensive bowel wall pneumatosis as a rare complication of chemotherapy
(arrow).
FIGURE 4
Coronal MDCT
demonstrating gas
locules in an oedematous left iliacus
muscle (arrow)
secondary to a
retroperitoneal sigmoid perforation.
FIGURE 3
Axial MDCT demonstrating a post-operative large
bowel anastomotic leak as shown by locules of gas
and free fluid adjacent to the anastomosis (arrow).